Oil well liner incorporating reinforcement coating



March 24, 1970 J. A. DU MEE ETAL 3,502,145

OIL WELL LINER INCORPORATING REINFORCEMENT COATING Filed July 19, 1968 FIG.

INVENTORSI JOANNES A. DU MEE HANS KRAK HERMAN F. SCHWENCKE BY: M57

THEIR ATTORNEY United States Patent Office 3,502,145 OIL WELL LINER INCORPORATING REINFORCEMENT COATING Joannes A. Du Mee, Oldenzaal, and Hans Krak and Herman F. Schwencke, Delft, Netherlands, assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed July 19, 1968, Ser. No. 746,069 Claims priority, application Great Britain, Jan. 30, 1968, 4,642/ 68 Int. Cl. E21b 43/08 US. Cl. 166--227 6 Claims ABSTRACT OF THE DISCLOSURE An oil well installation including a liner comprising an inner metallic tube covered by a reinforced resinous material. Slots are formed in the liner through both the metallic material and resinous material to permit the flow of production fluid into the interior of the liner while at the same time preventing inflow of gravel and sand which surround the liner. The resinous material resists the corrosive action of the production fluid to maintain slot size integrity.

The present invention relates to a well installation arranged in a deep well and suitable for the recovery of valuable fluids from -a subsurface formation containing such fluids. More particularly, the invention relates to a well installation comprising tubular means extending from the top of the well to a subsurface level and further comprising a deep well liner mounted over an interval which at least partially coincides with the interval of the fluidcontaining formation.

Such deep well liner is used in production wells to prevent undesired matter such as sand grains or gravel from entering the well together with the fluids which are being recovered from the formation. Deep well liners of many types are known, the difference between these liners for the greater part consisting in the design of the openings through which the fluid being produced enters the liner and by which the undesired matter, such as sand grains or gravel, is to be retained. The present invention, however, relates to an improvement of a well installation provided with a deep well liner comprising a tubular metal member having slots of very small width cut in the wall of the member. When the liner is set in an open hole without using a gravel pack, the particles entrained by the fluid which is being recovered from the formation are sieved ofl by the slots when the fluid passes therethrough. When the liner is surrounded by a gravel pack, the gravel is prevented from entering the liner interior, whereas the fluid flows through the slots. The undesired sand grains from the formation are then retained by the gravel pack.

The filtering efficiency of the above-described type of prior art liner is very good. However, this liner has a drawback when being operated in corrosive environments. The side walls of the slots cut in the metal tube may then easily be eroded and corroded away, e.g., when the metal is steel, such as is normally used in oil wells. This increases the width of the slots, with the result that particles of increasing dimensions will pass through the slots and enter the well, where some of them will be carried upward by the flow of fluid passing through the well and separated from the fluid flow in the surface equipment, thereby choking the fluid-flow passage through the equipment and reducing the efliciency thereof. Particles of greater dimensions than the ones that are lifted by the fluid stream will remain in the lower part of the well, thereby choking the passage through the well and reducing 3,502,145 Patented Mar. 24, 1970 the flow rate of the fluid continuously until a production rate has been reached which is too low to produce the well economically. The well has then to be repaired and a new liner has to be installed. It will be appreciated that production of very aggressive or highly corrosive fluids via the well installation will increase the rate at which the liner has to be replaced.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a well installation suitable to be placed in deep wells, which is resistant to corrosive fluids as produced from formations communicating with such deep wells.

Another object of this invention is to provide a well installation comprising a deep well liner in which the rate at which the slots arranged in the wall thereof for passing fluid therethrough and sieving undesired particles from this fluid increase in size when fluids of a corrosive nature are passed therethrough is substantially diminished.

Yet another object of the present invention is to provide a well installation suitable for use in deep wells for the production of oil, gas or water from subsurface formations, which comprises a liner which is not easily damaged when being placed in the well, and which has only seldom to be replaced since it remains effective in contact with aggressive or highly corrosive fluids.

These and other objects have been attained according to the present invention by providing a well installation arranged in a deep well comprising tubular means extending from the top of the well to a subsurface level, and a deep well liner which is mounted over an interval at least partially coinciding with the interval of a fluid-containing formation. Said deep well liner comprises a tubular metal member closed at its lower end, said member having at least part of the wall thereof covered with a layer substantially consisting of a reinforced resinous material. The reinforcement thus employed consists of a corrosiveresistant material. A fluid-flow communication is provided between the exterior and the interior of the liner consisting of slots arranged inthe wall of the liner, which wall is formed by the reinforced resinous material and the tubular metal member.

The reinforcement in the resinous layer at least partially covering the Wall of the tubular metal member may be formed by fibers, which are in the form of matting or of rovings. Also, stainless steel, nickel, chrome or ceramic materials like alumina-silica, carbon, graphite, silicon carbide, boron nitride, boron and glass can be used. If desired, combinations of these reinforcements may be applied.

The slots may be parallelly arranged. The distance between the slots depends, i.e., on the thickness of the reinforced layer. The width of the slots are applied depends on the size of the grains to re retained.

The well installation according to the invention is a structure of great strength. It comprises a deep well liner which can easily be placed at the bottom of a Well by being connected to the lower end of a tubular string which is run into the well. The wall of the liner, since it comprises the metal body of the tubular element, is sufliciently strong to withstand the forces acting thereon when the liner is being lowered in the well. Once in the well, the liner is exposed to the aggressive fluid passing therethrough. The parts of the liner which are most liable to corrosion are formed by the walls of the slots, since at these places the fluid has a rather high velocity as compared to the velocity of the fluid passing through the central passageway formed within the tubular member. It will be appreciated that the reinforced resinous layer will not be attacked by the corrosive fluid. Thus the slots, where passing through the resinous layer, will not alter their width or size during the passage of the corrosive fluid. Those parts of the wall defining the slots, however, which are formed by the metal body of the tubular member will gradually corrode away. This does not, however, influence the sieving capacity of the liner, since the parts of the wall of the slots formed by the reinforced resinous layer remain unchanged.

DESCRIPTION OF THE DRAWING These and other objects of this invention will be understood from the following description taken with reference to the drawing wherein:

FIGURE 1 is a diagrammatic longitudinal view illustrating the installation according to the present invention with the liner thereof positioned in a well in the location where it penetrates a fluid-containing formation from which fluid is to be recovered;

FIGURE 2 is a cross-sectional enlarged view of a section of the liner of the well equipment as shown in FIG- URE 1 and taken along a slot formed in the wall of the liner in the direction of line 22 as indicated in FIG- URE 1;

FIGURE 3 is a view similar to that shown in FIGURE 2 but of an alternative form of liner.

Referring now to FIGURE 1 of the drawing, the well 1, of which only the lower part has been shown, penetrates through the cap rock formation 2 which is substantially impermeable to the fluid contained in the pore space of the producing formation 3 underlying the formation 2. The well 1 has an enlarged part or cavity 4 where penetrating the formation 3. The well equipment or installation arranged in the well comprises, at the location shown in FIGURE 1, a casing or tubular means 5 which is cemented to the formation 2 by a cement layer 6 filling the annular space between the outer wall of the casing 5 and the wall of the well 1. A packer 7 is set in the lower end of the casing 5 and arranged around the blank part 8 of a deep well liner 9. The annular space between the liner 9 and the formation 3 is filled with gravel 10. Further reserve gravel is stored in the annular space between the blank part 8 of the liner 9 and the casing 5. The gravel in the cavity 4 supports the wall of this cavity thereby preventing caving of loose material against the liner 9. The particles of the gravel pack 10 are prevented from entering the interior of the liner 9 by the slots 11 which are arranged in the wall of the liner 9. The width of these slots is so chosen that during the period that the gravel is circulated into the cavity 4, the particles bridge the slots 11, thereby building up a permeable layer over the entrane to each slot.

To describe the construction of the wall portion of the liner 9 and the manner in which the slots 11 are arranged therein, reference is now made to FIGURE 2. This figure shows a section taken over the wall of the liner 9 at a location of a slot in the direction as indicated in FIGURE 1 by the line 22.

The liner 9 comprises a steel tube 12 which, in the example as described, is of a cylindrical nature. Around this tube 12, a reinforced resinous layer 13 has been arranged, which in the example as described is formed by winding glass rovings impregnated with a curable resin around the outer wall of the tube 12. By glass rovings are meant a bundle of monofilaments, made of glass fiber, which have no or only a very small twist. This winding technique is well known in the art of manufacturing fiber reinforced tubes, and need not be described in detail. In the example as described an unsaturated polyester cross-linked with styrene or homologues may be used as resinous material.

After curing of the resin in the layer 13 incorporating the rovings wound around the tube 12, the slots 11 have been cut in the wall of the liner 9 by means of a normal slotting machine which has been designed for cutting slots in the known metal liners. The width of these slots has been chosen in relationship to the size of the gravel used in the well in which the liner is to be applied.

In an alternative arrangement (vide FIGURE 3) the reinforced resinous layer 13 is covered by a second resinous layer 14, which is not reinforced. The wall of the liner 9 is then formed by the metal tube 12, the reinforced resinous layer 13 and the resinous layer 14. The slots 11 are then cut through the tube wall 12 and the two layers 13 and 14.

It will be appreciated that any desired number of resinous layers may be utilized according to the present invention with one or more layers being provided with at least one reinforcement medium formed by windings of rovings or by matting which has been wrapped around the tube 12 or around a previously applied resinous layer. For example, a second reinforced resinous layer (not shown) may be arranged around the resinous layer 14 (FIGURE 3).

As stated above, any combination of reinforced resinous layers, if desired combined with non-reinforced resinous layers, may be arranged around the tube 12. The slots 11, however, are always cut through the whole combination of resinous layers (reinforced and non-reinforced) as well as through the tube wall 12.

As can further be seen from FIGUURE 1, the liner 9 consists of two parts 9A and 9B which are interconnected by a coupling member 15 which may be provided with screw threads cooperating with screw threads (not shown) arranged on the respective ends of the parts 9A and 9B. Alternatively, any desired known type of connector means may be utilized for this purpose. The lower end of the part 9B is closed by a closing member or closure means 16 which is screwed to this lower end.

Part of the present well equipment on installation is mounted in the well 1 during the drilling operations in this well. After the required depth has been reached, the easing 5 which forms a part of the tubular means of the present invention is lowered in the well 1 to the required depth and cemented in place (vide cement layer 6).

After forming the cavity 4 (e.g., by an underreaming operation), the liner parts 9A and 9B are screwed together by coupling means 15, and the lower end of the liner part 9B is closed by screwing the closing member 16 thereto. Subsequently, the liner 9 is suspended at the top of the well and provided with the equipment normally used for setting liners with gravel pack (such as liner hanger-packer, wash pipe, cross-over tool). The liner 9 is then lowered in the well 1 by means of a tubular string (not shown) until the liner 9 has reached the desired location. During its travel downwards, the liner 9 is often in forceful contact with the inner wall of the casing 5. When placing the liner 9 in the cavity 4 it may be pressed with great force to the bottom of the cavity 4. However, no damage will be done to the liner 9 since the metal tube 12 around which the resinous layer (or layers) has (or have) been wound is in itself sufliciently strong to withstand such rough treatment.

After the liner 9 has been placed, the gravel pack 10 is circulated into the cavity 4 in one of the manners known per se. Subsequently the packer 7 is set and the well is completed by the usual arrangement. Then the well is ready for production. By reducing the pressure in the cavity 4 (e.g. by pumping action, opening the Well) or by injecting fluids in adjacent wells, a flow of production fluid is created which flows out of the pore space of the formation, through the pore space of the gravel pack 10 and via the slots 11 of the liner 9 into the interior of the liner 9, from where the production fluid is displaced in an upward direction to the top of the well.

The corrosive action of the fluid, due for instance to its salt content, will affect the metal parts of the tube 12 which are exposed to the fluid. Conseqeuntly the parts of the wall of the slots 11 which are formed by the tube 12 will corrode away. Prolonged exposure of the tube 12 to the action of the corrosive fluid results in a weakening of the tube 12 or even in a total disintegration thereof. As, however, the resinous layers (such as layers 13 and 14) as well as the reinforcements of such layers are resistant to the corrosive action of the fluid, the parts of the wall of the slots 11 which are formed by these layers will not be attacked by the fluid. The width or size of the slots where cut in the resinous layers will thus not be liable to an increase, and the filtering action of the liner 9 will consequently remain unimpaired by the corrosive fluid, even if this fluid is supplied to the liner over a very long period of time.

If the metal tube 12 has been weakened by corrosion, or been corroded away locally in total, the lateral load on the liner 9 exerted by the gravel pack 10 and the formation 3 will have to be taken up by the resinous layers. As at least one of these layers is reinforced, the tube thus formed by the slotted resinous wall is sufliciently strong to withstand such forces.

It will be appreciated that the invention is not limited to the embodiments as shown in the drawing by way of example. If desired, the resinous reinforced wall may instead of being applied to the outside of the metal tube, also be located on the inner wall of this tube, or on both the inner and outer walls of this tube. Further, the arrangement of the slots need not be as shown in the drawing. Any other type of pattern may be applied. The walls of each slot may be parallely or conically situated or disposed. In the latter case, the slot walls may either converge or diverage towards the interior of the liner.

The rovings which are described as a reinforcement for the resinous layer 13 may be replaced by matting, i.e., a fabric of glass fibers. If desired, rovings and matting may be combined in a single resinous layer or in adjacent resinous layers.

The application of the well equipment is not restricted to wells which are provided with gravel-filled cavities in the fluid producing formation. Any other type of completion may be used. Thus the liner may be set in a nongravel packed well, or in a perforated casing. In the latter case a gravel pack may be arranged within the casing and around the liner.

If desired, the liner 9 need not be packed off against the casing 5. If desired the packer unit 7 may be omitted or replaced by a packer-hanger unit or by any connection or supporting means suitable for the purpose.

The material which is used for the metal pipe may be formed by steel, aluminum or any other metal or metal composition suitable for the purpose.

Any type of curable resin may be applied for the resinous layers. Besides the polyester as already mentioned, epoxy resin or formaldehyde condensates may e.g., be used. The resin is applied either in liquid form or in powderous form to the reinforcement which is being wound on the pipe 12. A suitable curing agent may be added to this resin. If superimposed layers are applied, these layers may be based on different resins and/ or comprise different reinforcement materials.

Although the liner 9 as shown in FIGURE 1 consists of two parts 9A and 9B, any other number of parts may be applied. Any connection means suitable for the purpose may be applied instead of the screw coupling as shown in FIGURE 1. As the corrosion of the liner 9 will for the majority thereof take place around the slots 11, there is no need for an interconnection of the resinous layers of the adjacent parts 9A and 9B. If desired, however, these adjacent resinous layers may be connected together by wrapping over the adjoining ends of these layers and over the coupling 15 a matting which is impregnated with a curable resin. Thus, the reinforced resinous liner elements provided with slots 11 will not fall apart when tube 12 and the coupling 15 have been corroded away. Normally, however, this precaution is not necessary, provided that a sufliciently large area of each resinous layer near each end thereof is not provided with slots, and the resinous layers or at least the resinous layers directly covering the tube are firmly attached to the wall of the tube 12, thus preventing the corrosive fluid from entering between the resinous layers and the metal tube wall. In another manner, those parts of the metal not covered with resinous layers may be coated with a corrosion resistant paint.

While this invention has been described with particular reference to preferred embodiments thereof, it should be understood that the forms illustrated herein have been selected to facilitate the disclosure of the invention rather than to limit the number of forms which it may assume, and various modifications, adaptations and alterations may beapplied to the forms shown to meet the requirements of practice without departing from the spirit or scope of the present invention.

We claim as our invention:

1. An installation for use with a production well extendinginto a fluid-containing formation, said installation comprising:

tubular meas extending from the top of said well to a subsurface level;

liner means depending from said tubular means and positioned within said well at least partially coextensive with said fluid-containing formation, said liner means defining an interior chamber;

said liner means including a tubular metal member closed at its lower end, said member having at least part thereof covered by a layer substantially consisting of a resinous material reinforced by a corrosion-resisting material; and

a plurality of slots formed in said layer and said tubular metal member to provide communication between the interior chamber defined by said liner means and the space in the well outside said tubular metal member whereby production fluid may flow from said fluidcontaining formation into said interior chamber.

2. The installation according to claim 1 wherein said corrosion-resisting material comprises glass fibers.

3. The installation according to claim 1 wherein said corrosion-resisting material comprises material in the form of rovings.

4. The installation according to claim 1 wherein the tubular metal member comprises a plurality of tubular metal units releasably connected in an end to end manner.

' 5. The installation according to claim 1 including a layer of non-reinforced resinous material covering the layer of resinous material reinforced by a corrosion-resisting material and wherein said plurality of slots are formed through the layer of non-reinforced resinous material, the layer of reinforced resinous material and the tubular member.

6. A liner adapted for insertion into a producing well in the vicinity of a fluid-containing formation, said liner comprising:

a metal cylinder defining an interior chamber adapted to receive production fluid from said well for conveying said fluid upwardly from said well, said cylinder having a lower end;

closure means connected to the lower end of said cylinder;

a layer of resinous material surrounding at least a portion of said metal cylinder, said layer incorporating reinforcing corrosion-resistant material; and

slots means formed in said liner through said cylinder and said layer whereby production fluid may flow from said fluid-containing formation into said interior chamber.

References Cited UNITED STATES PATENTS 2,837,032 6/1958 Horsting 166-227 2,969,840 1/1961 DAudiffret et al. 166-227 3,099,318 7/1963 Miller et al. 166-227 JAMES A. LEPPINK, Primary Examiner US. Cl. X.R. 166-236 

